10 replies to this topic

[l8tbreakr]

I'm looking to add a sensor to my traqmate system for throttle position. Has someone come up with a packaged string pot and mount for the miata? Several of the other systems like Stack or Racepak have their sensors or dealers but TM doesnt have an easy solution. Ideas? Thanks!

[NigelStu]

Any of the other companies sensors can work, you just have to figure out the throttle angle vs output voltage equation - pretty easy to do.

String pots can be mounted conveniently with a small plate you bolt onto the same spot that holds the throttle cable on the intake manifold. Rotary style takes a bit more work but are far less expensive (R-T is one place that sells these).

[forestdweller37]

I've installed plunger pots below the throttle pedal in a couple of STS (That's autocross class) Miata. I could post up some information on how I did it if anyone's interested.

-Chris

[fishguyaz]

chris,
please post up whatever you can.
pictures, and links to parts would be appreciated.
i need to do this in my SM,the TP is the one thing i do find lacking in the traqmate with my traqmate systems data.
thanks

[forestdweller37]

chris,
please post up whatever you can.
pictures, and links to parts would be appreciated.
i need to do this in my SM,the TP is the one thing i do find lacking in the traqmate with my traqmate systems data.
thanks

Ok.

Here are a couple photos of my installation. (Please forgive my poor photography. I was very dark under the dash...)



The plunger potentiometer can be purchased here:

http://www.4qd.co.uk...ts.html#plunger

or here:

http://www.race-tech...avel_8_969.html

The pot is positioned using the OEM throttle stop bolt and acts as an additional return spring on the pedal.

The only down side I've encountered with this installation is a slight dip in the data when the driver's foot pushes the pedal from side to side at WOT. It's not so much that it really detracts from the quality of the data. I thought about having a little "button" made to fit on the plunger rod to alleviate the issue, but never got around to it.

Hope this helps.

-Chris

[l8tbreakr]

.

[l8tbreakr]

I decided to go with a string pot connected via a bracket I made and bolted to the throttle cable attachment point as suggested. The bracket didn't take me long to fab up and the install looks pretty clean. I threw a couple of photos here for others to reference for ideas in the future. I just mocked up a piece of coat hanger for a rotating pin until I can get down to the store for a proper nut/bolt.

I am having a problem getting it working right though. It's a standard 5v string pot, with the car's motor not running I show a min-max voltage range of 1.29v-2.54v by manually actuating the throttle with the car off, or by manually actuating the string pot with the car running (but not revving the motor). But if I monitor the signal voltage by actually revving the motor, it moves up a little bit from 1.35 but not much (like a tenth of a volt), and then doesn't scale up any further. I have a steady 4.64 voltage reference off the Traqmate, and have also monitored a steady 12v input directly from the car's fuse box (string pot is rated to 30v). I've eliminated wiring or connectors as an issue by verifying with voltmeter at different points and also changing out wires, and have tried introducing a 1k ohm / 1 watt resistor on the voltage input as well as the ground wire. It's strictly an issue with the motor revving, and assume then the alternator output is negating signal variance (?). Although my input voltage does appear constant regardless of RPM. Anyone know what would cause this and how I can address it?

Many thanks!

Attached Files

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[NigelStu]

I have a steady 4.64 voltage reference off the Traqmate, and have also monitored a steady 12v input directly from the car's fuse box (string pot is rated to 30v).

I'm going to guess its a grounding or other wiring issue. I'm not sure exactly how you have this wired in, but the above sounds like you have 2 power inputs? 5V ref from Traqmate and 12V from the car? Its a little unclear.



The string pots I've seen have 3 wires, looks like the same unit you have. 5v reference, ground and sensor output. 5v ref and ground should both go through the Traqdata box.


If this is how you have this wired in, look into interference. What are the sensor wires running near? Try re-routing or changing over to a shielded cable if you are parallel with any other wiring (like sharing the hole in the firewall with the main harness).



Only other thing I can think of is something screwy happening (and unlikely) with vibrations or grounding of the sensor case somehow. If the 1st 2 doesn't fix it, get a helper. Unbolt the string pot from the intake manifold and hold it in your hand (near the mounting point) while you have your helper activate the throttle with the engine running.



Nice looking install with the plate.

[l8tbreakr]

[quote name='NigelStu' timestamp='1298919086' post='3332']
I'm going to guess its a grounding or other wiring issue. I'm not sure exactly how you have this wired in, but the above sounds like you have 2 power inputs? 5V ref from Traqmate and 12V from the car? Its a little unclear.
[/quote]

Just one power input at a time. I've used the TM 5v, the TM 12v, and the car's 12v. Should have been clearer on that.


[quote]
The string pots I've seen have 3 wires, looks like the same unit you have. 5v reference, ground and sensor output. 5v ref and ground should both go through the Traqdata box.
[/quote]

Yes, you're correct - 3 wires. I've tested that way, and also tried isolating a different ground (thinking the TD ground wasn't good) and different power and ground (just to isolate the power and ground off the TD). Been bitten by bad grounds before, always worth a check.


[quote]
If this is how you have this wired in, look into interference. What are the sensor wires running near? Try re-routing or changing over to a shielded cable if you are parallel with any other wiring (like sharing the hole in the firewall with the main harness).
[/quote]

Good point, I'll look into that. The wire is a Cat 5 twisted pair wire so no shielding but it does have twist which should reduce EMI, but still worth running a different power wire to be sure.


[quote]
Only other thing I can think of is something screwy happening (and unlikely) with vibrations or grounding of the sensor case somehow. If the 1st 2 doesn't fix it, get a helper. Unbolt the string pot from the intake manifold and hold it in your hand (near the mounting point) while you have your helper activate the throttle with the engine running.
[/quote]

I've done that - with the car on I can activate the wire without the throttle, and it actually worked. It's one when the motor revs that it stops. But you gave me another idea - I doubt it, but wonder if maybe the sensor needs to ground its case and my painted bracket is an insulator.

[quote]
Nice looking install with the plate.
[/quote]

Thanks man. Funny, I thought that was going to be the time consuming part!

[l8tbreakr]

Problem solved with an external voltage regulator. I successfully tested with an 18v battery on that first weekend so I was confident everything was wired correctly but it was clear from testing with a voltmeter that my source voltage wasn't stable and so the sensor was producing an unstable voltage out. Running voltage straight off chassis is not ideal because the voltage is unstable due to alternator rpm and voltage fluctuating, and near as I can tell the 5v and 12v feeds off the TM are simply unstable. I don't think this is a fault of Traqmate, but rather I've had it for a few years and somewhere along the line probably fried or broke something. I installed regulator from Mouser - very small device, maybe 1"x2" and cost $35. Wired it in using chassis power and ground and everything worked immediately.


Thanks to everyone for your suggestions, and hopefully this resolution will benefit others.

[AJG]

For anyone looking for that voltage regulator, here's the info:

http://www.mouser.co...KkthiCnHotg9Nc= - It's Mouser PN EC5BE03

I got this tip from Ranger over on the Spec E30 board, and it has been working great for me.

To the guy who PM'd me, I hope you see this. I changed accounts and can't respond to your PM directly.